1. Field of the Invention
The present invention relates to an X-ray computed tomography apparatus of a type in which an X-ray tube rotate around a subject to be examined.
2. Description of the Related Art
Conventionally, an X-ray computed tomography apparatus has been widely used to take a tomographic image of a subject to be examined. The mainstream of current X-ray computed tomography apparatuses is a type in which an X-ray tube and X-ray detector continuously rotate around a subject to be examined.
A gantry incorporates a motor which rotates/drives an annular rotating frame (support) on which an X-ray tube and X-ray detector are mounted. With this arrangement, the X-ray tube and X-ray detector serve to detect transmitted X-rays while applying X-rays to a subject to be examined from various directions, and the X-ray computed tomography apparatus reconstructs a tomographic image of the subject on the basis of the detected data. The gantry is provided inside with a slip ring and brush for, for example, supplying power to the X-ray tube, the X-ray detector, and the like which rotate, and extracting various kinds of signals (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 8-280661), a bearing (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 5-305075), a pulley and belt for transmitting the power generated by the motor (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-112995), and the like.
In general, the gantry is provided with a tilting mechanism which tilts the frame so as to change the slice angle of scan with respect to a subject to be examined (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-52689). This tilting mechanism comprises a monitor, rollers, sprockets, chains, and the like as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 5-91995.
A couch is provided with a driving means for driving a top in the vertical and horizontal directions, as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-126083. The power generated by this driving means is transmitted to the top through pulleys, belts, and the like.
As described above, various kinds of consumable parts and parts that require cleaning, such as slip rings, brushes, bearings, pulleys, belts, rollers, sprockets, and chains, are used for an X-ray computed tomography apparatus. In order to maintain the apparatus in a proper state, it is important to perform maintenance such as cleaning and inspection of the apparatus and replacement of consumable parts at proper timings.
The maintenance of an X-ray computed tomography apparatus has often been performed in a cleaning cycle, inspection cycle, and part replacement cycle set on the basis of reference data created by a maker or the like. In this case, reference data is data concerning the durability of parts and the like, which is created by a maker or the like for, for example, the calculation of the lifetime of an apparatus. This reference data is generally created on the basis of an inspection method unique to each maker, load values, and the like. Such inspection methods have not been unified. For example, in some cases, inspection is done by applying an actual load to an apparatus after a target part is built in it. In other cases, inspection is done while a given standard load value is applied to an apparatus.
According to such a conventional maintenance service, maintenance is performed in a uniform cycle in every hospital regardless of the frequency of use of an X-ray computed tomography apparatus in the hospital. Therefore, the following problems may arise. With regard to an X-ray computed tomography apparatus with a high frequency of use, since a given part greatly wears out in the same period, a proper maintenance timing may be lost. If the apparatus fails due to this, it cannot be used during a repair period. This causes inconvenience to the user. With regard to an X-ray computed tomography apparatus with a low frequency of use, since a given part wears out little in the same period, maintenance may be done before a proper maintenance timing, inflicting unnecessary cost on the user.
As described above, a maintenance timing has been set on the basis of the use period of an X-ray computed tomography apparatus. However, a maintenance timing should be determined on the basis of the frequency of use of the apparatus and, more specifically, the actual operation amount of each part constituting a driving portion. For conventional X-ray computed tomography apparatuses, however, maintenance timings could not be determined on the basis of such a criterion.
In addition, in consideration of the fact that many parts used for an X-ray computed tomography apparatus are developed as parts dedicated to the apparatus, the number of parts as samples in a durability test is greatly limited (for example, about one to three) under the present situation. Therefore, the reliability of reference data is not necessarily high. For example, makers and the like have prevented the occurrence of problems in apparatuses by setting relatively short maintenance cycles. In some cases, a technician of an X-ray computed tomography apparatus designates a maintenance timing on the basis of his/her experience at his/her own discretion. The validity of the maintenance timing is inevitably questionable.
Performing maintenance at the timing based on such data with low reliability and validity will lead to the waste of service provision time and labor on the customer engineer side, and will lead to the waste of cost and the risk of apparatus failure on the user side.